In recent years, there has been proposed a monolithic circuit for an active matrix liquid crystal display device, in which a scan signal line driving circuit and a data signal line driving circuit are integrally provided on a single TFT substrate. Such a monolithic circuit can contribute to miniaturization of a body of the display device and simplification of a production process of the display device. However, in contrast, such a monolithic circuit has been one of factors causing a reduction in yield rates. This is because an entire display panel would be determined as a defective product in a case where a driving circuit has a failure.
Patent Literature 1 etc. have disclosed a technique for preventing, with a simple arrangement, a reduction in yield rates due to such a failure in the driving circuit. FIG. 20 is a view illustrating a schematic arrangement of a liquid crystal display device of Patent Literature 1. The liquid crystal display device includes two systematic scan signal line driving circuits 13 and 15 and two systematic data signal line driving circuits 17 and 19. Therefore, (i) in a case where one of the two scan signal line driving circuits 13 and 15 has a failure, the liquid crystal display device can switch over the one having a failure to the other one having no failure (i.e. a normal one, which is hereinafter referred to as “redundant circuit” in some cases) and (ii) in a case where one of the two data signal line driving circuits 17 and 19 has a failure, the liquid crystal display device can switch over the one having a failure to the other one having no failure (redundant circuit). This arrangement is simple but capable of increasing yield rates by reducing a percentage of defective display panels.